Match each navigation or surveillance system to its primary function or operating principle:

Systems:
1. Primary radar
2. Secondary surveillance radar (SSR)
3. Distance measuring equipment (DME)
4. Global positioning system (GPS)

Functions:
A. Calculates slant range by measuring the transit time of paired radio pulses
B. Computes three-dimensional position using time-of-arrival signals from a satellite constellation
C. Detects targets by transmitting radio energy and measuring reflected echoes
D. Interrogates an onboard transponder to obtain coded identity and altitude replies

Question

Match each navigation or surveillance system to its primary function or operating principle:

Systems:
1. Primary radar
2. Secondary surveillance radar (SSR)
3. Distance measuring equipment (DME)
4. Global positioning system (GPS)

Functions:
A. Calculates slant range by measuring the transit time of paired radio pulses
B. Computes three-dimensional position using time-of-arrival signals from a satellite constellation
C. Detects targets by transmitting radio energy and measuring reflected echoes
D. Interrogates an onboard transponder to obtain coded identity and altitude replies

Accepted Answer

1-C, 2-D, 3-A, 4-B. Primary radar relies on reflected radio energy; SSR relies on a cooperative transponder reply. DME calculates range from signal timing and reports slant range. GPS calculates position from satellite signals processed by the user receiver. Each system provides different information and has distinct limitations.

**Key takeaway:** Know whether a system measures bearing, range, identity, altitude, or position.

**Glossary:** **Primary radar**: non-cooperative reflected-signal surveillance; **GPS**: Global Positioning System.

Explanation

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